6 Asymmetric Encryption and Hybrid Encryption

This chapter covers:

  • Asymmetric Encryption can be used to encrypt secrets to a public key.
  • Hybrid Encryption can be used to encrypt large amounts of data to a public key.
  • The standards for Asymmetric and Hybrid Encryption.


  • Chapter 4 on Authenticated Encryption.
  • Chapter 5 on Key Exchanges.

You’ve learned about authenticated encryption in Chapter 4, which is a form of symmetric encryption. Authenticated encryption allowed you to encrypt data to someone else who shared the same symmetric key. This is an extremely useful cryptographic primitive, yet in the real world, there exist many situations where different peers do not have a shared secret. Chapter 5 introduced asymmetric cryptography and how key exchanges allow two participants who are aware of each other’s public key to derive a shared secret in the open. This chapter bridges asymmetric cryptography with symmetric cryptography, showing you how you can encrypt to a person with whom you do not share a secret yet, as long as you know their public key.

Le’ts get started!

6.1  What is Asymmetric Encryption?

The first step to understanding how to encrypt a message to someone is asymmetric encryption (also called public-key encryption). In this section you will learn about this cryptographic primitive and its properties.

Let’s take a look at the following real-world scenario: encrypted emails.

6.2  Asymmetric Encryption in Practice and Hybrid Encryption

6.3  Standards for Asymmetric Encryption and Hybrid Encryption

6.3.1  Textbook RSA

6.4  Attack of the Chapter: RSA PKCS#1 v1.5

6.5  Asymmetric Encryption with RSA-OAEP

6.6  Hybrid Encryption with ECIES

6.7  Summary